GGT1 and hyperinsulinemic hypoglycemia, familial, 4: GGT1 deficiency is a rare autosomal recessive disorder that can lead to disturbances in glutathione homeostasis, weight loss, reproductive defects, mental retardation, and cataracts (in the absence of GGT, the absence of GSH in the body leads to a depletion of cysteine, which is not compensated for by hepatic synthesis; the lack of cysteine limits glutathione synthesis, and the concentration of glutathione in the eye is only 39% of normal, leading to free radical accumulation and the induction of cataract formation).